Furnace-regulator system



Mar. 27, V1923.

. C. A. BODDIE.

FUHNACE REGULATOR SYSTEM.

FILED NOV. 13, 1919.

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Patented Mar. 27, 1923.

UNITED STATES PATENT OFFICE.

CLARENCE A. BODDIE, F PITTSBURGH, IPENNSYLVANIA, ASSIGNOR T0 WESTING-HOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION 0F PENN-SYLVANIA,

. FURNACE-REGULATOR SYSTEM.

Application led November 13, 1919. Serial No. 337,687. i

To all whom it may concern.'

Be 'it known that I, CLARENCE A. Bonnin, a citizen of the United States,and a resident of Pittsburgh, inthe county of Alle- 5 gheny and State ofPennsylvania, have invented a new and useful Improvement inFurnace-Regulator Systems, of which the following is a specification.

My invention relates to regulator systems and particularly to regulatorsystems for governing the operation of the movable electrodes inelectric furnaces.

One object of my invention is to providel a furnace-regulator systemthat shall govern each movable electrode, not only in ac'- cordance withthe current ,flowing through it but also in accordance with thepotential difference obtaining between the neutral point of thev supplycircuit and the bath of material being treated to maintain equal heatingeffects by the various electrodes, and that shall be so operated as toprevent hunting action.

In operating electric furnaces of the movable-electrode type, and,particularly, if the furnace is connected to a three-phase supplycircuit, considerable trouble is generally` experienced in obtainingequal heating effects by the various electrodes or in obtaining a fixedratio of heating effects by the various electrodes. Such uneven heatingeffects are liable toy be experienced if a charge having an unevenresistance throughout its structure is being treated in the furnace. Incase the electrodes of the furnace produce unequal heating effects, thelining of the furnace is not subjected to an even temperature and,consequently, the length of time which the furnace may be operatedwithout repairs is greatly reduced. Thus, the producing of'unequalheating effects by the various .electrodes is liable to impair the valueof the material being treated in the furnace and, moreover, to` `cause amore` rapid deterioration of the furnace than would be effected if theratio of the work performed. by the various electrodes were v maintainedsubstantially constant.

In an electric furnace constructed in acelectrode is provided with meansfor soadjusting it that the ratio of work ,performed by the variouselectrodes shall. vbe maintained substantially constant, irrespectivecordance with my invention, each movabley of the operating conditions ofthe furnace, and,moreover, means is provided for in suring the systemagainst hunting action.

' More specifically, my invention relates to an electric furnace havingthree movable r electrodes which are connected to a threephase supplycircuit. Each of the electrodes is provided with a motor for raising andlowering it and each motor is provided with a regulator for operating itto maintain the ratio of the heating 'effect produced by the associatedelectrodes to the heating effects produced by the remaining electrodessubstantially constant. Each of the regulators embodies an electromagnethaving two windings which operate two rent passing through the secondwinding of each electromagnet will have lsuch phase relation to thecurrent passing through the first windingv as to add to, or subtractfrom, the energizing effect of the firstwinding, according to whetherthe associated electrode is being operated to produce a greater or aless than normal portion of the heating effect of the furnace. Moreover,means is provided which is operated by the two switches for varying theenergization of the current winding in each regulator to prevent huntingaction.

This invention is an improvement on the furnace-regulator systemdisclosed in the patent application Serial No. 288,832. filed April 9,1919, by Robert D. Evans and assigned to the Westinghouse Electric &Manufacturing Company, and reference may be had to the above applicationfor au vanalysis of the phase relation of the currents owing through thecurrent and potential windings of 'the main magnet-.of the regulator.

'ulator system constructed in accordance with my invention. a

Referring to the drawing, an electric furnace 1, comprising a receptaclecontaining a bath of material` 3, is provided with three movableelectrodes 4, 5 and 6 which are-directly connected to a three-phasesupply circuit comprisin conductors 7, 8 and 9. Each of the movab eelectrodes 4, 5 and 6 is provided with a motor for raising and loweringit and a regulator for so governing the electrode motor as to maintainthe ratio of heating effects by the various electrodes substantiallyconstant: Inasmuch as the electrode motors and the associated regulatorsare similar in construction and operation, it is deemed suflicient toillustrate and describe but one motor and one regulator, namely, themotor and regulator which are associated with the movable electrode 6.

A motor 10, comprising an armature 11 and a field winding 12, isprovided for raising and. lowering the electrode 6 to maintain asubstantially constant heating effect by the electrode. The fieldwinding l2 is directly connected to an auxiliary supply circuitcomprising conductors 13 and 14, and the armature 11 -is selectivelyconnected to the supply conductors 13 and 14 by means of two switches 15and 16. The motor 10 is mechanically connected-to the electrode 6 inanysuitable manner, as by means of a winding reel 17 and a fiexibleconnector 18 which passes over a pulley 19.

A regulator 20, comprising a main control electromagnet 21 and thel twoswitches 15 and 16, is provided for governing the operation of the motor10, not only in accordance with the current fiowing through theelectrode 6 but Aalso in accordance with the potential obtaining betweenan artificial neutral point of the supply circuit and the' bath ofmaterial 3 being treated in the furnace. The main controlelect-romagnets for the regula-tors which govern the operation of theelectrodes 4 and 5 are designated by the reference characters 23 and 22.

The main control electromagnet 21 em.- bodies a current winding 24having taps 25,

26 and`27 extending from it, a potential winding 28 and a co're armature29. The

core armature 29 is provided with a dash pot 30 for adjusting the speedof its operation and is pivotally connected to a contact arm 31. Thecurrent winding 24v is connected to the three-phase supply conductor 9by means of a transformer 32 in order to be energized in accordance withthe current flowing through the electrode 6. The potential winding 28 isconnected across two conductors 33 and 34 which are respectivelyconnected to the bath-of material 3 being treated and an artificialneutral point of the 'When two windings are so connected, the neutralpoint of the three-phase circuit 1s obtained 'by a tap from the winding36 which divides the winding 36 in the ratio of 2 to 1. In brief, theneutral point of the supply circuit is represented by thepotential'existing in the winding 36 at a point one-third of 'its lengthfrom the point of connection to the winding 35. The tap 37 from thewinding 36 is directly connected to the conductor 34. Inasmuch as theabove described means for obtaining an artificial neutral point in asupply circuit is well-known, it is deemed unnecessary to make acomplete analysis of the potentials obtaining in .the two windings whenso connected. i

The main control magnet 22 is provided with a current winding 38, whichis connected to the three-phase supply conductor 8 bymeans of a currenttransformer 39, and with a potential winding 40 which is connectedacross the conductors 33 and 34. The.

main magnet 23, which is associated with the electrode 4, is providedwith a'current winding 41 which is connected to the threephase supplyconductor 7 by means -of a current transformer 42, and a potentialwinding 43 which is connected across the conductors 33 and 34. l

The contact arm 31 is fulcrumed at 44 and carries a main contact member45 which engages contact members 46 and 47, according to the operativeposition of the main magnet 21. members 45 and 46,v a circuit iscompleted from the supply conductors 13 and 14 for operating the switch16 and, upon engagement between' the contact members 45 and Uponengagement between the contact,

47, a circuit is completedl for operating the switch 15.

The switch 15 comprises a winding 48 and a core armature 49 which iscontrolled by it.

The core armature 49 is directly connected to two switch members 50 and51 and two interlock switch members 52 andv 53. The two switch members50 and 51 serve to-connect the armature llacross the supply con?`ductors 13 and 14 for effecting counter-clockwise rotation of the motor10. The counterclockwise rotation of the motor 10 raises the electrode 6to decrease the current flow` main magnet to prevent any hunting actionwhen the electrode is being raised from the bath of material.

The switch 16 comprises a winding 54 and an armature 55 which iscontrolled by it. The armature 55 is directly connected to two switchmembers 56 and 57 and two interlock switch members 58 and 59. The twoswitch members 56 and 57 serve to connect the armature 11 across. thesupply conductors 13 and 14 for operating the motor 10 in a clockwisedirection to lower the electrode 6 in the furnace. The interlock switchmember 59, upon operation of the switch 16, serves to open ashort-circuit which normally obtains across that portion of the winding24 which is included between the taps 26 and 27. Such operation of theinterlock switch member 59 serves tol prevent any hunting action whenthe electrode 6 is being lowered in the furnace.

.'When the two switches 15 and 16 are deenergized, the two interlockswitch members 52 and 58 complete an energizing circuit from the supplyconductors 13 and 14 for a brake relay 60. `The brake relay 6()completes a dynamic-braking circuit for the armature 11 through aresistor 61.

Assuming that the electrode 6 is performing more than its normal portionof the work of the furnace 1, there is either an increased current flowthrough thel electrode 6 or an unbalancing of the phase relation of thecurrent flow through the electrodes 4, and 6, the amount of which willbe indicated by the potential obtaining between the neutral point of thesupply circuit and the potential of the bath of material 3 being treatedin the furnace. If an increased current flows throuoh the electrode 6,the energization of the winding 24 willbe increased to operate thecontact arm 31 and effect engagement between the contact members 45 and47 and, if an unbalanced phase relation obtains, the winding 28, whichis energized in accordance with the potential existing between theneutral point of the supply circuit and the bath of material 3, will beenergized to assist the winding 24 in moving the contact arm 31 toeffect engagement-between the lcontact members 45 and 47. Uponengagement between the contact members 45 and 47, a circuit .iscompleted from the supply conductor 13, through the contact arm 31,contact members 45 and 47 and the winding 48 of the switch 15, to thesupply conductor 14. Thereupon, the switch is operated to complete acircuit through the armature 11 for operating the motor 10 in acounterclocki wise direction. The circuit through the armature 11 istraced from the supply conductor 13, through the switch member 51,armature 11 and the switch member 50 to the supply conductor 14.

In case no means were provided for pre- Venting any hunting action, themain control magnet 21 would be controlled solely by the circuitconditions of the electrode 6 and, consequently, the main magnet wouldnot be operated to separate the contact members and 47 and stop themotor until normal conditions obtained in the electrode circuit.Consequently, the inertia4 of the various movingparts of the regulatorand the inertia of the armature would cause overtravel and, accordingly,would raise the electrode 6 above the desired point to obtain normaloperating conditions. In order to prevent such overtravel, and theconsequent hunting action, the interlock switch member 53 is operatedsimultaneously with the operation of the motor 10 for short-circuiting aportion of the winding 24 to decrease the energization of the mainmagnet 21 and, consequently, to effect a separation of the contactmembers 45 and 47 just prior to the obtaining of normal conditions inthe electrode circuit.

In case the electrode 6 is performing less than its normal portion ofthe work of the furnace, the energization of the winding 24 is decreasedor the winding 28 is energized by a smaller current or by current havingsuch power factor as to oppose the action of -the current flowingthrough the winding 24 and thus permit the operation of the contact arm31 to effect engagement between the contact members 45 and 46. Uponengagement between the contact members 45 and 46, a circuit is completedwhich extends from the supply conductor 13 through the Contact arm 31,contact members 45 and 46 and the winding 54 to the supply conductor 14.Thereupon, the swltch 16 is operated for connecting the armature 11across the supply conductors 13 and 14 to operate the motor 10 in aclockwise direction. The clockwise rotation of the motor 10 lowers theelectrode 6 to obtain normal operating conditions.

In order to prevent any hunting action when the electrode is beinglowered in the -furnace, the interlock switch member 59 is operated,simultaneously with the operation of the motor 10, to open theshort-circuit which normally obtains across that portion of the winding24 which is included between the taps 26 and 27. Thus, the energizationofth'e main magnet 21 is increased and its setting is so changed` as to,effect separation of contact members 45 and 46 just prior to `theobtaining of normal conditions in the circuit of the electrode 6.

yAlthough the operation of but one electrode has been described indetail, itshould be noted thatthe main control magnets 21, 22 and 23 areoperated to simultaneously adjust the three electrodes 4, 5 and 6 tomaintain the ratio of work performed -by them substantially constant.The current esv -flowing through the potential windings 28,

g 40 and 43 will have phase relations relative to the currents flowingthrough the wind-v ings 24, 38 and 4l to assist or to oppose the actionof the windings 24, 38 and 4l, according to the heating effects of theassociated electrodes. For a complete analysis of the yrelations of thecurrents flowing through the potential and the currentwindings,reference may be had to the application Serial No. 288,832, abovereferred to.

Modifications in the system and arrangement and location of parts may bemade Within the spirit and scope of my invention,

and such modifications are intended to be y covered by the appendedclaims.

I claim as my invention:

1. In a furnace regulator system, the combination comprising a polyphasesupply circuit, a plurality of movable electrodes connected thereto,means for automatically contro-lling each of said electrodes to equalizethe heating effect of the various electrodes, and automatic means forpreventing hunting action.

2. In a furnace-regulator system, the combination comprising a polyphasesupply circuit, a plurality of movable electrodes conlnected thereto, amotor for raising and lowering each of said electrodes, means foroperating each motor to equalize the heating effects produced by thevarious electrodes, and automatic means associated with each electrodevfor preventing hunting action.

3. In a furnace-regulator system, the combination comprising athree-phase supply circuit, three movable elec-trodes connected thereto,a motor for raising and lowering each of-said electrodes, means forselectively operating said motors in accordance with the characteristicsof the current supplied to the electrodes to equalize the heatingeffectsA produced by the various electrodes, and automatic means forpreventing hunting action.

4. In a furnace-regulator system, the com- I bination comprising asupply circuit, three movable electrodesconnected to the supp-lycircuit, means for adjusting said electrodes in accordance with thedifference in potential between` the bath of material being treated andthe neutral point of the supply circuit, and means for insuring thesystem against hunting action.

5. In a furnace-regulator system, the combination comprising a supplycircuit, three movab-le electrodes connected-to the supply circuit,means for adjusting said electrodes in accordance with the difference inpotential between the bath of material being treated and theneutralpoint of said supply circuit and in accordance with the current suppliedtothe electrodes, and means for preventing hunting action. 6. In afurnace-regulator system, the combination comprising a three-phasesupply circuit, three movable electrodes connected to the supplycircuit, means controlled by the potential existing between the neutralpoint of the transformer and the bath of material being treated formaintaining the ratio of work performed by the various electrodessubstantially constant, and'means for insuring the system againsthunting action. i 7. In a furnace-regulator system, the combination of apolyphase supply circuit, a

ciated electrode with respect to the other electrodes, and means forvarying the energization of each current winding to prevent huntingaction.

8. In a furnace-regulator system, the combination with a three-phasesupply circuit, three movable electrodes connected to said circuit, anda motor for operating each of said electrodes, of means comprising amain magnet having a potential winding for neutralizing the potentialbetween the electrodes and the bath of material being treated, saidpotential winding being energized in accordance with the difference inpotential between the neutral point of the supply circuit and the bathof material being treated, and means for controlling said electromagnetto prevent hunting action.

9. In a furnace-regulator system, the combin'ation with a three-phasesupply circuit, three movable electrodes connected to. said supplycircuit, and a motor for raising and lowering each electrode, of meanscomprising a main magnet having a current and a potential winding forcontrolling each electrode to maintain'the ratio of work performed bythevarious electrodes substantially constant, each of said current windingsbeing energized in accordance with the cur-` between the neutral pointof said supplyl circuit and the bath of material being treated, andmeans for varying the energizatioln of said. current windings to preventhunting action'. A

10. In a furnace-regulator system, the combination with a polyphasesupply circuit, a movable electrode connected to said supply circuit,and a motor for raising and lowering said electrode, of means comprisinga main magnet having a current and a potential Winding for operating theelectrode to maintain a substantially constant heating effect by theelectrode arc, said potential windingbeing energized in accordance withthe potential obtaining between the neutral point of the supply circuitand the bath of material being treated, and means for varying theenergization of the current winding to prevent hunting action.

11.1n a furnace-regulator syst-em, the combination comprising aplurality-of movable electrodes, means for maintaining al constantcurrent flow through the electrodes and for equalizing the potentialsacross the various electrode arcs, and automatic means for preventinghunting action.

1Q. In a furnace-regulator system, the combination comprising aplurality of movable electrodes, means comprising a pluralcoilelectromagnet operatively associated with each electrode for maintaininga predetermined ratio of heating el'ects by the various electrodes andmeans for preventing hunting action.

In testimony whereof7 I have hereunto subscribed my name this 27th dayof Oct.,

CLARENCE A. BODDIE.

